Press



oct. 1', 1946. F, DAY 2,408,379

' K vPRESS Filed Aug. 7, 1944 3 Sheets-Sheet 2unlllllllllllnllllllllllnllllllllnllnll, I

2; zg v INVENTOR.

l y Y L. F. DAY

Oct'. 1, 1946.

PRES S Filed Aug,` '7, 1944 3 Sheets-Sheet Z @il Y INVENTOR Luiher FDayBY v 2f Patented Oct. 1, 1946 S l PATENT oFFlcE PRESS p Luther F. Day,Hawthorne, Calif., vassignor to North American Aviation, Inc.

' 'Application August '1, 1944, serial No. 548,383

This invention relates to improvements inA pneumatic presses and hasasits general object toiprovide a press of relatively simple and in-rexpensive construction which is capable of delivering a rapid successionof strokes having ex-V treme accuracy of stroke limit. A further objectof the invention is to provide a press which elimi- Vnates the wear andtear lupon the clutch used in `the conventional flywheel and crank-typepress.v A further object is to provide vapress adapted to deliver astroke of maximum terminal power with' a minimum expenditure of energyin the lover-al1 operation o f the press. lA further object is toprovide a press which permits of rapid variation in the'speed ofoperation thereof without wasting power and without straining themechanism. y'

rThe invention contemplates a lm eumatically powered, toggle strokedelivery mechanism type of press and aims particularly to provide apress of this type whichiscapable of delivering twice as many workingstrokes per rcycle of motor op-v eration, and which provides for greateraccuracy of stroke and correspondingly more uniform accuracyin theworkpiece, than has been possible inyprior presses of this' generaltype. To this end', the inventioniprovides for'through-center operationofthe toggle'mechanism by the pneumatic servo motor, so that the workingstroke of f the ram terminates inthe middle rather than at the end of` amovement of the servo motor.

This arrangement produces the double advantage of improving the accuracyand uniformityk of the length of the ramstroke and'also ldoubles the`number of ram strokesper cycle of servo motor operation. A furtherobject of the invention is to provide novel and improved controlmechanism for a double acting 'servomotoL wherein Vautomatic control isderived from thedevice actuated by the servo motor.

Another object is to provide a kpress which may be converted from singlestroke to continuous operation lsimplyfby turning a valve handle.

Another object of the invention is'to provide a pneumatically-poweredpress 'which can readily be synchronized with a cooperating machine suchas, for example, an automatic feeding. device.4

Like` reference characters designate similar parts in the several which:f

Fig. 1 is a front elevation of the press; Fig. 2 is a section taken onthe line Fis. 1;

l 1 claim." (c1. Y10o-'10) Fig. 3 illustrates diagrammatically theoperating circuit; Y.

Fig.`4 is a detail oi the valve arrangement taken on line 4-\-4 of Figs.1 and 5; and

Fig. 5 is a side elevation partially in section of the valve shown inFig. 4.

shaft 6 is Secured to Y in the frame As an example of one form in whichtheinvention maybe embodied, I have shown in the drawings a light punchpress comprising a frame I having parallel side members provided withslide Ways 3*--3 in which is mounted, for vertical reciprocation, a ram2. Movement is transmitted to the ram 2 by toggle mechanism comprisingpairs, of toggle arms 4.' andV 5-5 pivotally joined together by a shaft8 and pivoted respectively at-their remote ends to the ram 2 bytrunnions and to the frame I by a shaft 6. The the arms 4 and journaledA tool 'la may be supported in the ramr2 and adapted to cooperate with asuitable mating tool mounted on the bed 1b of the press.

Vertical reciprocating movement of the ram 2 is produced by alternatelymoving the pivotal joint between the toggle arms rst to one side andthen to theother side of the axis of ram movement, and for thispurpose-I provide a pneumatic servo motor comprising a cylinder pivotedat |2 to the frame and havingva double acting piston 3| (Fig. 3) towhich is fixed a piston rod l0 linked to the shaft 8 by a cross head 9.It may be noted at this point that the stroke of the tool 1a isdeliveredr when the piston 3| is intermediate the ends of its stroke. Inthe single stroke type of operation that has previously characterizedtoggle presses of this type, it has been impossible to terminate thepiston stroke with suicient accuracy at the exact point of on-centeralignment of the toggle arms so as to attain uniformityv of ram stroke.By .moving the toggle through center Yand delivering the ram kstrokegreater accuracy andstriking powerin the ram views of the drawings, in Vstroke and at the same time provide for double the number of ram strokesper cycle ofV servo motor operation.

Retracting ymovement of the piston 3| is'effected by introducingV airthrough a feed line 29Y intovthe chamber 30 formed between the one sideof the piston 3| and the cylinder -Extending movement of the piston 3|is effected by introducing air under pressure through a line 33 into thechamber 32 delined between the opposite side of the piston 3| and thecylinder When air is being introduced through the line 2,9 into the 3chamber 3i), air from the chamber 32 is exhausted through the feed line33, and vice versa.

For reversing the flow through the lines 25 and 33, I provide a slidevalve including a casing 25 having ports 28 and 34 with which the lines29 and 33 communicate, having -an inlet 25 communicating with a. sourceof air under pressure, and having discharge vents 35 and 42respectively, the former adapted to vent air from the line 33 while theinlet 26 is delivering air to the other line 29 and the latter adaptedto vent air v from the line 29 when the inlet 26 is delivering air tothe line 33, Slidably mounted in a bore 50 in the casing 25 is a valveplunger 38` having spaced valve ports 21 and 35 respectively (eachenlarged at the surface of the plunger so as to bridge the space betweenthe inlet 26 and the ports 23, 34 respectively) the port 21 beingadapted at one limit of plunger movement to establish communicationbetween the inlet 26 and the line 29 while the port 35 establishescommunication between the line 33 and the vent 35, and the port 35 beingadapted .at the other limit of plunger movement to establishcommunication between the inlet 2G and the line 33 while the port '2lestablishes communication between the line 29 and the vent 42.

On the respective ends of the plunger 38 are pistons 31 andl whichoperate respectively in cylinders 45 and 43 formed in the respectiveends of the casing 25. For moving the slide valve toward the right asviewed in the drawings, air is introduced from a line 22 into thecylinder 43 to act against the piston 39 while air behind the piston 39is bled through a vent 44. Simultaneously, air in the cylinder 45 isvented through the line 2I in response to movement of the piston 31; andair enters the cylinder 45 through a vent 4I to ll the space behind thepiston 31. In the movement of the plunger in the opposite direction, theflow is reversed.

The flow through the lines 2i and 22 is ccntrolled by a pilot valvecomprising a cylindrical casing I mounted on the frame I and encirclingone end of the shaft 6 which is oscillated by the upper toggle arms 4.The air lines 2| and 22 connect respectively with ports I9 and 28circumferentially spaced in the casing I5. The shaft 6 has a centralbore I6 which is connected toa source of vair under pressure by afitting I1 threaded into the end of the shaft 6, a. rotatable couplingI'Ia, and a feed linellb. A passage I8 in the shaft 5 delivers air fromthe bore I6 to the port IS when the arms 4 are at one limit of theirmovement and to the port 24 when the arms 4 are at the other limit oftheir movement."v When the passage I8 is thus delivering lair to theline 2-I the line 22 is vented through a Vent I8b in the periphery ofthe shaft 5, registering with the port 20. Vand opening into the end ofthe shaft 6. When the passage I8 is delivering air to the line 22, theline 2i is vented through av vent lila,

4 its function until the next half cycle of operation of the servo motorhas taken place, and the slide valve continues to function until thathalf cycle of operation is completed, the pilot valve being the whileshifted for the next half cycle of operation.

The invention lends itself readily to synchronization with a cooperatingmachine without .change in the above-described mechanism. All that isnecessary in 'order to achieve such synchronization is to control thepilot valve feed line I1b from the cooperating machine. For example,where it is desired to synchronize the `press with a feeding device suchas that shown in Fig. 3, including a slide 41 operated by any 'suitablesource of reciprocating movement (such as the crank shaft 48 driven by amotor 49 and similar tothe Vent i811 but located in the shaft 6 on 'theopposite shown.

The pilot valve operates to shift the plunger 38 from one limit of itsmovement to the other limit thereof prior to any substantial movement ofthe servo motor piston 3|. With the slide valve thus shifted, the pilotvalve has completed side Vof the passage VI8 as connected to the slide41 by a pitman 56) it is only necessary to provide a control valveoperated by the slide 41 when the latter has completed its cycle ofoperation, and for rthe purpose of illustrating such a valve, .I haveshown a valve including a casing 5I having an oscillatory valve element52 therein voperated by an arm 53 which in turn is moved in onedirection by the slide 41 and in the other direction by a spring 54. Byconnecting the line I1b and a feed line v55 in properly spacedrelationship to the casing 5|, the valve may be made to cut olf the flowof air under pressure to the pilot valve except for a short interval atthe limit of retracting movement of the slide 41, during which intervalthe air may be supplied to the pilot valve for a suicient length of timeto reverse the slide valve. While I have shown a power-driven source ofmovement for the slide -41 it is to be understood that the slide 41could, if desired, be operated manually and the press .wouldautomatically operate in respense to the manual operation of the slide.It is also to be understood that while the movement of thev cooperatingmachinehas been described, for illustrative purposes, as a`reciprocatingmovement, that it need not necessarily be that type of movement butcould be any other type, such r as, vfor example., rotary movement.

The foregoing may be taken as illustrative of one form in which theinvention may be embodied, it being 'my intention to cover in my claimthe use of any equivalent arrangement or apparatus.

I claim as my invention:

In a press, a frame, a ram adapted 'to have linear reciprocatingmovement with reference to said frame, a toggle comprising a pair ofarms -pivotally joined to each other, the remote ends of one of said"arms being attached to a trunnion member which is journaled in saidframe., the remote end of the other arm being vpivoted to said ram, adouble acting pneumatic 'servo motor linked to the pivotal joint betweensai-d 'armsjair circulating means for delivering air 'under pressure toone end of said servo motor while eX-y hausting air from the oppositeend thereof, and means for reversing the ilow in saidV circulating meansVat predetermined limits of reciprocating movement of said servo motor,comprising a valve having an oscillating valve element comprising anextension of saidv trunnion 'and receiving movement therefromj v LUTHERDAY.

